Ultrasonic impact treatment for useful life improvement of downhole tools

ABSTRACT

The useful life of a downhole tool is improved through application of an ultrasonic impact treatment. In an example method, operational parameters of an ultrasonic impact treatment device are selected based upon the one or more physical characteristics of the downhole tool. The ultrasonic impact treatment device is configured to correspond to the selected operational parameters. A residual compressive stress layer is then induced along a surface of the downhole tool using the configured ultrasonic impact treatment device, thereby improving the useful life of the downhole tool.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to useful life improvement for downhole tools and, more specifically, to an ultrasonic impact treatment (“UIT”) to improve the life of downhole tools.

BACKGROUND

Currently, roller burnishing and shot peening are applied for inner diameter/outer diameter treatment of drill collars and other downhole tools. Each process, however, has its own limitations. For example, the shot peening process is limited by the shallow compressive layer/lower magnitude of induced compressive stress, while roller burnishing (or deep rolling) is limited by the relatively complex nature of the process as well as limited availability in remote drill sites. Moreover, these processes are not suitable for machining tool features having corners or sharp bends, each of which has a direct effect on the useful life of the downhole tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for improving the useful life of a downhole tool according to one or more example methods of the present disclosure.

FIG. 2 is a schematic diagram illustrating a contact probe and tip of an ultrasonic impact treatment device according to one or more exemplary embodiments of the present disclosure.

FIG. 3A is a graph plotting stress-number of cycle (S—N) fatigue curves for an as-machined downhole tool as compared to a downhole tool that has undergone an ultrasonic impact treatment of the present disclosure.

FIG. 3B is another graph comparing the surface finish of a downhole tool that has undergone an ultrasonic impact treatment according to the present disclosure with the surface finish of an as-machined downhole tool.

FIG. 3C is a schematic diagram illustrating the behavior of fatigue crack propagation within a threaded profile of a downhole tool that has undergone an ultrasonic impact treatment according to the present disclosure.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments and related methodologies are described below as they might be employed in an ultrasonic impact treatment method to improve the useful life of downhole tools. In the interest of clarity, not all features of an actual implementation or methodology are described in this specification. It will be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments and related methodologies disclosed will become apparent from consideration of the following description and drawings.

As described herein, ultrasonic impact treatment methodologies of the present disclosure can be applied to extend the useful life of downhole tools by inducing compressive stress layers along any desired surface of the downhole tool using an ultrasonic impact treatment device. Through use of the disclosed methods, the useful life of the downhole tool may be improved, such as by increasing the fatigue life, corrosion resistance or weld crack resistance of the downhole tool. Exemplary methodologies achieve the foregoing changes in mechanical properties by introducing ultrasound energy into the surface of the downhole tool through a surface impulse contact probe (pin or ball probe, for example), also known as ultrasonic impact treatment. The ultrasonic impact treatment device introduces deformation on the surface layer which, in turn, induces a compressive residual stress. Since the contact probe can be customized to a desired shape, the ultrasonic impact treatment can be applied to any desired surface of the downhole tool. As the downhole tool is being used, the induced compressive layers prevent crack growth in the tool's subsurface layers, thus increasing its fatigue life, corrosion resistance or weld crack resistance. Accordingly, through use of the disclosed methods, various mechanical/physical properties of the downhole tool may be improved. For example, the fatigue life of a target surface of the downhole tools may be improved by as much as four to five times as compared to an as-machined surface of the downhole tool. With reference to FIGS. 1-3C, various ultrasonic impact treatment methods will now be described.

FIG. 1 is a flowchart 100 of a method for improving the useful life of a downhole tool according to one or more example methods of the present disclosure. Flowchart 100 improves the useful life of the downhole tool using an ultrasonic impact treatment device. Suitable downhole tools may be, for example, measurement while drilling tools, logging while drilling tools, or formation evaluation while drilling tools. Examples of such tools include DrillDoc®, GeoTap-IDS®, SLD® and ALD®, each of which is commercially available through Halliburton Energy Services, Co. of Houston, Tex. One example of a suitable, commercially available ultrasonic impact treatment device is an Esonix® UIT Portable System, manufactured by Applied Electronics of Birmingham, Ala. However, other commercially available or proprietary ultrasonic impact treatment devices may also be selected for use with the described ultrasonic impact treatment methods. The selected ultrasonic impact treatment device may be operated manually or precisely through use of robotic methods to ensure the desired accuracy and surface coverage are attained.

Referring again to the flowchart of FIG. 1, at block 102, a downhole tool is provided having various physical characteristics such as, for example, a thread root radii (for an API thread type, for example), a corner radii, a tool material (such as non-magnetic austenitic stainless steel or Ni-based alloy, for example), and a material hardness. In certain embodiments, the downhole tool is first secured. The downhole tool may be secured, for example, using a fixture. Such use of a fixture is particularly suitable in embodiments that employ precise robotic modes of application, whereby the ultrasonic impact device is operated by robotic mechanisms. Alternatively, the downhole tool may also be secured using fixtures in situation where a handheld approach is used, whereby the ultrasonic impact device is operated by hand.

At block 104, operational parameters of the ultrasonic impact treatment device are then determined based upon the physical characteristics of the downhole tool. Operational parameters may include, for example, device settings and/or physical characteristics of the ultrasonic impact treatment device. Physical characteristics of the ultrasonic impact device may include, for example, the contact probe tip geometry and tip material types. The probe tip geometry and tip material types may be optimized, for example, based upon the physical characteristics and the radii call out on the downhole tool. Similarly, the operational parameters, such as operating frequency and oscillating amplitude, may be optimized based upon the stress analysis performed at the physical characteristics of the downhole tool (e.g. at the corners) and the depth of compressive layers sought to be induced along the downhole tool's surface. The operational parameters may further include, for example, at least one of an operating frequency, oscillating amplitude, treatment travel speed, output power range, or excitation voltage. In certain exemplary embodiments, the operating frequency may be in the range of 20-50 kHz, oscillating amplitude in the range of 20-40 microns, treatment travel speed in the range of 0.3 m/min.-1.5 m/min, output power range of 200-1800 VA, and excitation voltage in the range of 60-110V. However, such operational parameters may be adjusted as necessary for any given application.

At block 106, the ultrasonic impact treatment device is configured to correspond to the operational parameters of the downhole tool. In one implementation, the configuration of the ultrasonic impact treatment device is achieved using one or more user-selectable settings of the ultrasonic impact device, which can be adjusted or otherwise set according to the desired or expected operational parameters necessary for the given downhole tool.

At block 108, the ultrasonic impact treatment device is then used to induce residual compressive stress layers along one or more desired surfaces of the downhole tool, thereby improving the useful life of the downhole tool. In certain implementations, compressive layer depths up to 0.100″ have been imparted on a target surface of a downhole tool according to this aspect of the method. Examples of these target surfaces of the downhole tool that may be treated include the threads, welded portions, or exterior portions of the tool (e.g. external pockets along the tool or corners). Thereafter, the downhole tool treated according to an embodiment of the method outlined in FIG. 1 may then be used in a downhole operation as desired. The operation and performance of the tool may be improved as a result of the change in mechanical or physical properties as described with reference to the method of FIG. 1 and elsewhere in this disclosure.

In certain embodiments, the physical characteristics of the downhole tool described so above may also be used to determine the geometry of the contact probe (alternatively referred to in the art as the indenter) of the ultrasonic impact treatment device, as well as the materials used in the device. The geometry of the ultrasonic impact treatment device may include, for example, the number of contact probes, the contact probe diameter, contact probe tip diameter or treatment angle.

FIG. 2 is a schematic diagram illustrating a contact probe 18 of an ultrasonic impact treatment device according to one or more exemplary embodiments of the present disclosure. Contact probe 18 includes a diameter 20 and tip geometry 22. Physical characteristics of the ultrasonic treatment device may include the various contact probe materials of various hardnesses, such as pure metals or metal alloys or composites of ceramic and metallic materials (i.e. “cermets”). In one embodiment, the geometry and materials associated with the ultrasonic impact treatment device may include, for example, the selection of a single or multiple in-line contact probe (i.e., number of contact probes), a contact probe diameter in the range of 0.1-0.25 inches, a contact probe tip geometry in the range of 0.010 inches-any customizable tip radii, a vertical treatment angle, and a contact probe material hardness in the range of 40-70 HRC.

In another example method, the ultrasonic impact treatment may be applied to the downhole tool before, or as step of, repairing the ultrasonic impact treatment device. For example, if a downhole tool has been corroded due to the downhole environment (mud, for example), an ultrasonic impact treatment may first be conducted along the tool's surface according to the presently disclosed principles. After the ultrasonic impact treatment device has been performed, a protective hard-layer coating, such as a high-velocity oxygen fuel spray coating, may be applied. Alternatively, the ultrasonic impact treatment may be conducted on the tool (and then the coating applied) before the tool is ever deployed downhole. In yet another alternative methodology, the entire internal diameter of the downhole tool may be treated using the ultrasonic impact treatment device in order to protect the tool from internal diameter corrosion cracking in those areas experiencing high chloride levels.

As demonstrated above, exemplary methodologies of the present disclosure can be used to impart desired physical or mechanical characteristics to a downhole tool. For example, the fatigue life of the downhole tool is improved when compared to as-machined downhole tools, as can be seen in FIG. 3A.

FIG. 3A is a graph plotting S—N fatigue curves (Stress—Number of cycles) for an as-machined downhole tool as compared to a downhole tool that has undergone an exemplary ultrasonic impact treatment of the present disclosure. In this graph, the tool bending stresses ranging between 40,000 to 140,000 psi are plotted versus the tool rotating bending cycles ranging between 100,000 to 1,000,000,000 cycles. FIG. 3A is a semi-log plot where the Y-axis is the bending stress and the X-axis is the cycles plotted on a logarithmic scale. The S—N fatigue curve for the treated samples show significant improvement over their as-machined counterpart. For example, if one were to pick a given bending stress of 110,000 psi, the as-machined sample lasted only 500,000 cycles before failure while the samples treated with the exemplary ultrasonic impact treatment lasted up to about 5,000,000 cycles before failure. This is almost an order of magnitude higher. One could easily visualize a similar trend for other bending stresses. Over a wide range of bending stresses, one can summarize that the ultrasonic impact treated samples on an average improve the fatigue life by a minimum of four to five times over the as-machined samples.

In addition, the surface finish is also improved as shown in FIG. 3B. FIG. 3B is another graph illustrating the surface finish improvement of a downhole tool that has undergone an exemplary ultrasonic impact treatment of the present disclosure as compared to an as-machined downhole tool. Fatigue under bending loads usually initiate from the surface since surface stresses are the highest. Fatigue also initiates at areas of higher stress concentration which may be internal features such as, for example, metallic inclusions in the microstructure or, external, such as rough surfaces. Thus, a smooth surface has much lower concentration of stress risers and, hence, is desirable if a component undergoes fatigue loading.

Still referring to FIG. 3B, the X-axis on the graph is the trace length at the thread root where the respective surface treatments have been performed. The Y-axis is the Roughness Average (Ra) value that is expressed in micro-inches. As understood in the art, Ra is the arithmetic mean of the absolute departures of the roughness profile from the mean line of measurement. The lower the number, the smoother the surface. The three values in the boxes below Ra indicate that three such measurements were made for each type of surface treatment and the average was reported below the three values. Accordingly, FIG. 3B illustrates that these surface treatments significantly improve the as-machined surface and consequently the improvement on the fatigue endurance of the downhole tool. Moreover, the beneficial effects of the present disclosure also extend to stress corrosion cracking resistance since the compressive stress layer would work against the tensile stress that is necessary to complete the stress corrosion cracking resistance.

In addition, the present disclosure provides a useful effect on the direction of the fatigue crack initiation/propagation. FIG. 3C is a schematic diagram illustrating the behavior of fatigue crack propagation within a threaded profile of a downhole tool that has undergone an exemplary ultrasonic impact treatment of the present disclosure. With reference to FIG. 3C, an exemplary threaded profile 30 of a downhole tool that has undergone ultrasonic impact treatment is illustrated having a surface 32. Unlike as-machined tool surfaces, the fatigue crack initiations 34 occur at a deeper sub-surface layer and the crack propagation is at an incline. As a result, fatigue crack initiations 34 take longer to span the entire cross-section area of the subsurface and, thereby, result in tool failure. This phenomenon, in addition to the compressive layer that is generated as a result of the ultrasonic impact treatment, assists in achieving the improved fatigue life of the downhole tool.

Moreover, the present disclosure provides portability of application where, for example, a portable ultrasonic impact treatment device may be used offshore or in remote areas (repair and maintenance facilities, for example). As such, the fatigue life of the downhole tool threads or physical characteristics may be improved. In addition, the present disclosure may also be used to combat the cracking susceptibility at the heat affected zones on welded connections along the tool. In such methodologies, the ultrasonic impact treatment is conducted after the welding is completed, thus introducing the compressive layers that combat subsequent cracking.

A few exemplary optimized sets of parameters for specific thread types and/or other physical characteristics will now be described. In one methodology, the ultrasonic impact treatment is applied to the threads of a downhole tool using the following parameters: operating frequency of ˜40 kHz; oscillating amplitude of ˜20 μm; probe tip diameter of ˜0.125″; probe tip radii of ˜0.020″; robotic mode; probe tip hardness of 50 HRC; treatment angle of 45°-90°; measured compressive layer depth of ˜0.012″; and a compressive layer of ˜40-50 ksi.

In another exemplary methodology, the ultrasonic impact treatment is applied to one or more physical characteristics (corners, edges, etc.) using the following parameters: operating frequency of ˜25 kHz; oscillating amplitude of ˜30 μm; probe tip diameter of 0.125″; probe tip radii of ˜0.060″; robotic mode; probe tip hardness of 56 HRC; treatment angle of 45°-90°; measured compressive layer depth of ˜0.070″; and a compressive layer of ˜90-100 ksi. These and a variety of other optimized parameters may be used with the present disclosure.

Although various embodiments and methodologies have been shown and described, the disclosure is not limited to such embodiments and methodologies and will be understood to include all modifications and variations as would be apparent to one skilled in the art. Therefore, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims. 

What is claimed is:
 1. A method to improve useful life of a downhole tool, the method comprising: providing a downhole tool having one or more physical characteristics; selecting operational parameters of an ultrasonic impact treatment device based upon the one or more physical characteristics of the downhole tool; configuring the ultrasonic impact treatment device to correspond to the selected operational parameters; and to inducing a residual compressive stress layer along a surface of the downhole tool using the configured ultrasonic impact treatment device, thereby improving the useful life of the downhole tool.
 2. A method as defined in claim 1, wherein the surface of the downhole tool comprises threads of the downhole tool.
 3. A method as defined in claim 1, wherein the surface of the downhole tool comprises welded portions of the downhole tool.
 4. A method as defined in claim 1, wherein the surface of the downhole tool comprises external pockets along the downhole tool.
 5. A method as defined in claim 1, wherein the one or more physical characteristics of the downhole tool comprise at least one of a thread root radii, corner radii, downhole tool material, or the material hardness of the downhole tool.
 6. A method as defined in claim 1, wherein configuring the ultrasonic impact treatment device further comprises determining at least one of a geometry or material used for a contact probe of the ultrasonic impact treatment device based upon the one or more physical characteristics of the downhole tool.
 7. A method as defined in claim 6, wherein the geometry or material used for the contact probe comprises at least one of a contact probe diameter, treatment angle or contact probe material hardness.
 8. A method as defined in claim 1, wherein the operational parameters of the ultrasonic impact treatment device comprise at least one of an operating frequency, oscillating amplitude, treatment travel speed, output power range or excitation voltage.
 9. A method as defined in claim 1, wherein the method is used to repair a downhole tool whose protective coating has been eroded, the method further comprising re-applying the protective coating atop the residual compressive stress layer.
 10. A method as defined in claim 1, wherein the residual compressive stress layer is induced along an internal diameter of the downhole tool.
 11. A method as defined in claim 1, wherein the downhole tool is used in a downhole operation.
 12. A method to improve useful life of a downhole tool, the method comprising inducing a residual compressive stress layer along a surface of the downhole tool using an ultrasonic impact treatment device, thereby improving the useful life of the downhole tool.
 13. A method as defined in claim 12, wherein the method is used to repair a downhole tool whose protective coating has been eroded, the method further comprising re-applying the protective coating atop the residual compressive stress layer.
 14. A method as defined in claim 12, wherein the residual compressive stress layer is induced along an internal diameter of the downhole tool.
 15. A method as defined in claim 12, further comprising configuring operational parameters of the ultrasonic impact treatment device based upon one or more physical characteristics of the downhole tool.
 16. A method as defined in claim 15, wherein configuring the operational parameters further comprises determining at least one of a geometry or material used for a contact probe of the ultrasonic impact treatment device.
 17. A method as defined in claim 16, wherein the geometry or material used for the contact probe comprises at least one of a contact probe diameter, treatment angle or contact probe material hardness.
 18. A method as defined in claim 15, wherein the operational parameters of the ultrasonic impact treatment device comprise at least one of an operating frequency, oscillating amplitude, treatment travel speed, output power range or excitation voltage.
 19. A downhole tool produced using either of the methods of claim 1 or
 12. 